And Arsenal defender Mertesacker believes the tests they went through proved they have the collective will and resolve to be crowned world champions.

"They were three completely different games," said Mertesacker. "We suffered in the second. It was a real mental test, against Ghana, where we suffered and struggled.

"But we came back and equalised. That was a real test for us. Against the US we showed more personality and character and that was a real test because they have a great attitude and mentality.

"There were a lot of warnings from European teams, because teams with great character and mentality went though the group stage easily because they stick together.

"That's something we have to show as well, and we want to show the world we can cope with the different conditions."

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Mertesacker also believes the strength in depth of Germany's squad can give them an edge over their rivals now the tournament has entered the knockout stage.

"It's outstanding and we have great additions, players we can bring in to make a difference," said Mertesacker. "That makes it much easier. The selection is harder for the manager but he can count on every player because they all have quality.

"There will never be a lack of motivation because the mutual support in this team is really great and we try to take advantage. We have to. Otherwise we will suffer."

Asked about the teams that had impressed him most, Mertesacker said: "Those not with the best players but the ones with the best team performances, more from South America - Colombia, Costa Rica, Chile.

"They are always giving absolutely everything for every second, over 90 minutes. If you can't cope with that, you're out. If you show it for 60 or 70 minutes, it's not enough."